coding unit 4

What does the following code print?

int x = -4;

while (x < 0)

{

x++;

System.out.print(x + " ");

}

\-3 -2 -1 0

How many times will the following code print out the value of x?

public static void main(String\[\] args)

{

int x = 1;

while (x > 10)

{

System.out.println(x);

x--;

}

}

0 times

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Which statement can we use inside of a loop to end it?

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1. System.out.println;
2. break;
3. SENTINEL;
4. else;

2. break;

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Why does the following code produce an infinite loop? Choose the best answer.

public static void main(String\[\] args)

{

int x = 7;

while (x > 0)

{

System.out.println(x);

}

}

The loop doesn’t ever change the value of x in the loop, so it never ends.

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Why do we use while loops in Java?

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1. To break out of some block of code
2. To do something if a condition is true
3. To repeat some code while a condition is true
4. To repeat something for a fixed number of times

3. To repeat some code while a condition is true

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Which statement could be added to the while loop below so that it doesn’t run indefinitely?

public static void main(String\[\] args)

{

int x = 7;

while (x > 0)

{

System.out.println(x);

}

}

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1. A. You can add x-- after the print statement.
2. B. You can add x = -1 after the print statement.
3. C. You can add x++ after the print statement.
4. Both A and B above.

A and B

What will this while loop do?

while(true)

{

System.out.println("Hello");

}

Print Hello in an infinite loop

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Why do we use for loops in Java?

\

1. To break out of some block of code
2. To do something if a condition is true
3. To do something while a condition is true
4. To repeat something for a fixed number of times

4. To repeat something for a fixed number of times

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Consider the following loop, where n is some positive integer.

for (int i = 0; i < n; i += 2)

{

if (/\* condition to test \*/)

{

/\* perform some action \*/

}

}

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In terms of n, which Java expression represents the maximum number of times that /\* perform some action \*/ could be executed?

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1. (n + 1) / 2
2. n / 2
3. (n - 1) / 2
4. n
5. n-1

1. (n + 1) / 2

Which for loop will properly print “hello” 10 times?

A

for(int i = 0; i < 10; i++)

{

System.out.println("hello");

}

B

for(int i = 10)

{

System.out.println("hello");

}

C

for(int i = 0; i++; i < 10)

{

System.out.println("hello");

}

D

for(int i = 10; i < 0; i++)

{

System.out.println("hello");

}

A

What does the following code print?

for (int i = 2; i < 9; i++)

{

System.out.print(i + ", ");

}

2, 3, 4, 5, 6, 7, 8,

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Consider the mystery method below.

public static String mystery(String str1, String str2)

{

int index = str1.indexOf(str2);

return str1.substring(index, index + str2.length());

}

What is true about mystery?

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1. A. It may return a string that is equal to str2.
2. B. It may return a string that has no characters in common with str2.
3. C. It may return a string that is equal to str1.
4. Both A and C are true
5. None of these choices will be true.

A and C

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What is the general formula for traversing a String character by character?

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1. for(int i = 0; i < string.length(); i++)

{

String character = string.substring(i, i +1);

}


2. for(int i = 0; i

1

Given

String str = “RETRIEVER”;

int index = str.substring(1, 4).indexOf(“R”);

what is the value of index?

2

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Which of the following will execute *without* throwing an exception error?

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1. String str1 = “Golden”;

String str2 = “Retriever”;

if (str1.equals(str2))

{

System.out.println(“Golden Retriever!”);

}


2. String str1 = “Golden”;

String str2 = str1.substring(4); System.out.println(str1 + str2);


3. None of the above
4. A and B above.

A and B

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Consider the following method.

public void processString (String str)

{

str = str.substring(2, 3) + str.substring(1, 2) + str.substring(0, 1);

}

What is printed as result of executing the following statements (in a method in the same class)?

String str = "Frog";

processString(str); System.out.println(str);

Frog

What will this code produce?

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for (int j = 1; j

1 1 1 1
2 2 2
3 3
4

What does the following code print?

for (int i = 1; i < 6; i++)

{

for (int y = 1; y

A rectangle of 5 rows with 4 stars per row.

How many stars are output when the following code is executed?

\
for (int i = 0; i < 5; i++)

{

for (int j = 0; j < 10; j++)

{

System.out.println("\*");

}

}

50

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What is printed as a result of executing the following code snippet?

for (int k = 0; k < 25; k = k + 2)

{

if (k % 3 == 0)

{

System.out.print(k + " ");

}

}

0 6 12 18 24

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How often is the inner loop of a nested loop run?

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1. Infinitely
2. Twice as often as the outer loop
3. Each time the outer loop runs
4. One less time than the outer loop runs

3. Each time the outer loop runs

Consider the following code snippet. Is count < 5 always true, always false, or sometimes true/sometimes false at point 2?

int count = 0;

while (count < 5)

{

System.out.println("CodeHS Rocks!");

count++;

\
// point 2

}

sometimes true/sometimes false

Consider the following code snippet. Is count < 5 always true, always false, or sometimes true/sometimes false at point 1?

int count = 0;

while (count < 5)

{

// point 1

System.out.println("CodeHS Rocks!");

count++;

\
}

always true

Consider the following code snippet. Is count < 5 always true, always false, or sometimes true/sometimes false at point 3?

int count = 0;

while (count < 5)

{

\
System.out.println("CodeHS Rocks!");

count++;

\
}

// point 3

always false

How many times does the following loop iterate?

// x has been initialized with a positive int value

for (int count = 0; count

x+1 times

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Why is having efficient algorithms important?

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1. It reduces the cost of running a program.
2. It can improve the speed that programs operate.
3. It increases the speed of innovations.
4. Both 1 and 2.
5. Both 2 and 3.

both 1 and 2

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How many times does the following loop execute?

// x has been initialized with a positive int value greater than 5

int count = 5;

while (count < x)

{

count++;

}

x-5 times

How many times does the following loop iterate?

// x has been initialized with a positive int value

int count = 0; while (count < x)

{

count++;

}

x times